You should be able to drop an ATmega168 or ATmega8 (with appropriate bootloader) onto an Uno, with no other modifications (to the Uno.) You would have to either buy these chips with a bootloader pre-installed, or have some other mechanism for installing the bootloader.

In the "board" menu, you would need to select the board based on the chip and bootloader used, rather than using "Uno." So an Uno Board with atmega168 and the old bootloader would be called a "Diecimila ... with mega168"

OK, so if I install the bootloader using the Arduino as an ISP/breadboard method. I should then be able to use any of these chips. Right?How to I select what bootloader to install?

From what I can read the Atmega88 is not supported?Is the Atmega48 supported?

One more "kinda" related question.If i want to use the atmega chip outside the Uno board, but I want it to use it's internal clock. Do I need a special bootloader?

And if I install a bootloader on a chip using the Arduino as an ISP/breadboard method without a crystal. Will is be usable on my Uno running at 16mhz? Not sure if my question is clear?

google "todbot blog" and look for a good post on building standalone arduino clones with atmega8's and where to get bootloaders.

I believe you can use the arduino environment to program for the atmegas you mentioned as well. If you have a programmer to burn the bootloader you might consider using it to burn your sketch and forget about the loader alltogether.

using the internal oscillator rather than the external crystal is set with fuses on the chip. Once you've set the fuses correctly you could, conceivably, still use the chip in your uno - you'd need a custom boards.txt entry - see the todbot blog. This doesn't affect any other chips that you might plug in.

I have spent a lot of time fooling with attiny's, as have others here. The more I play with other chips, the more i respect the original decision to use the atmega8. It was a real sweetspot for capability vs size and it's grown nicely with the 168/328. What i mean by that is: consider sticking with the full-size processor for ease of use unless you need an awful lot of them.

Look at the boards menu on the Arduino IDE, these are the only processor/bootloader/speed options available for an unmodified Arduino IDE. You may burn the bootloader using any of the five devices listed in the burn bootloader menu.

If other AVR processors are desired or bootloaders you will have to venture into the land of command line AVRDUDE program, that can burn most any ATmel processor and use any bootloader hex file you are able to locate or write yourself, and can use a ton of different hardware programers.

Once done, you will have to have the needed modifyed files for the Arduino IDE if you wish to utilize your new chip/bootloader/speed combination with the standard IDE platform, or utilize standalone tools/other IDE platforms.

It can get a little complex, but if you clearly state the end condition of what hardware and what tools you you wish to use, there is usually a path to that goal.

those are all in the list. Note that the 48 won't support a bootloader.

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Method = breadboard with crystal connected to Uno board.

I have fumbled around with using arduinos as programmers with variable success. I eventually bought a programmer.

Once the bootloader is on are you going to plug these into the arduino to load a sketch then plug them into some other circuit to run in?

I'm a little leery of the 10mhz crystal, some of the arduino stuff is fine with oddball speeds, some of it insists on either 8mhz or 16mhz. Also, if these are factory fresh chips they're likely set up to run on the internal oscillator so you could skip the crystal on your breadboard.

As you note, I'm geographically close (Orleans) and I don't mind helping physically. You could mail me chips for programming or maybe a phonecall would help. PM me if you want to follow up.

That's not QUITE true. The 48 does not support a separate bootloader section, and the current bootloaders won't work on it, but it DOES have self-programmable flash, so it COULD support a bootloader of a sort...